Recently, scientists have described a resistant, quiescent population of leukemia cells that have limitless self-renewal potential. The identification of these "leukemia stem cells" (LSCs) provides an additional strategy in treating and preventing relapsed/refractory acute leukemia. One mechanism for resistance to treatment is the protection afforded LSCs via the interaction between stem cell derived growth factor (CXCL-12/SDF-1α) and its receptor, CXCR4. These interactions are implicated in chemotaxis, homing, and survival/apoptosis of hematopoietic stem cells and progenitor cells. All AML and ALL cells express CXCR4 and SDF-1α. AMD3100 (plerixafor, MOBOZIL®) is a bicyclam that blocks CXCL-12 binding to and signaling through CXCR4, thus disrupting tumor-stroma interactions and mobilizing leukemia cells from their protective stromal environment. Plerixafor is currently FDA approved for use in stem cell mobilization for autologous transplantation in hematologic malignancies. Clinical trials in adult patients with relapsed AML have demonstrated promising results when combining plerixafor with cytotoxic chemotherapy.